Salmon Poisoning in Bears:

• Neorickettsia helminthoeca, a rickettsial organism.
• This organism infects the trematode Nanophyetus salmincola. The trematode develops through two intermediate hosts, a snail and a fish, usually a salmonid fish. The final, mammalian, host, is infected when it eats an infected fish. (P507.2005.w5)
• The disease is associated only with the Pacific Northwest of North America, since this is the only area where the first intermediate host of the trematode, the snail Oxytrema plicifer, can live. (D251.9.w10)
• The disease only occurs if living flukes are present; the rickettsias are released/injected into the bloodstream after the adult fluke penetrates the mucosal lining of the gut. (D251.9.w10)
  • Dead flukes, in fish which has been cooked or frozen, cannot transmit the organism. (D251.9.w10)

• Neorickettsia helminthoeca (Tenericutes (Lacking cell-walls) (Division))

Clinical signs

• In two Helarctos malayanus - Sun bear at The Oakland Zoo, vomiting, anorexia, diarrhoea and lethargy. (P507.2005.w5)
  • Ultrasonography revealed mild ascites enlarged mesenteric lymph nodes and a dilated stomach. (P507.2005.w5)
  • Cytology of aspirated abdominal fluid: modified transudate, increased eosinophils. (P507.2005.w5)
  • Gastroduodenoscopy: stomach contained a large quantity of green fluid. The gastric mucosa showed patchy erythema. The duodenum "appeared thickened and pale." (P507.2005.w5)
  • Gastrointestinal biopsies: "severe lymphoplasmacytic and eosinophilic gastritis and enterocolitis, and erosive enteritis of the duodenal mucosa." (P507.2005.w5)
• Salmon poisoning was thought to be the cause of death for two Ursus maritimus - Polar bears in a Pacific Northwest (North American) zoo in 1982. (D251.9.w10)

Diagnosis

• Diagnosed on the basis of the identification of multiple large, gold-coloured, operculated trematode ova as those of Nanophyetus salmincola. (P507.2005.w5)
  • Note: Detection of Nanophyetus salmonica eggs requires flotation using a sugar solution, not fecasol. (D251.9.w10)
• Take a fine needle aspirate of enlarged lymph nodes, stain with Giemsa and examine microscopically for the intracytoplasmic rickettsial bodies. (D251.9.w10)
• Note: common symptoms in affected dogs include vomiting, lack of appetite, fever, diarrhoea, weakness, swollen lymph nodes and dehydration. (D251.9.w10)

Incubation

• About one week (signs occurred about a week after the bears had eaten live trout). (P507.2005.w5)

"Zoo bears fed raw or improperly frozen fish have contracted the disease, but the species most affected have been bears not native to the Northwest coastal areas (polar, sloth, Himalayan, and European brown)." (P507.2005.w5)

Treatment

• In two Helarctos malayanus - Sun bear at The Oakland Zoo: (P507.2005.w5)
  • Oxytetracycline 10 mg/kg intramuscularly once daily for 12 days, then doxycycline 10 mg/kg orally twice daily for 21 days. (P507.2005.w5)
  • Praziquantel 4 mg/kg intramuscularly once daily for three days, followed by a further dose of 12 mg/kg orally five days later. (P507.2005.w5)
  • Response to treatment: Gradual improvement of appetite starting within two days of the initiation of treatment. Faeces returned to normal consistency within seven days of starting treatment. (P507.2005.w5)
• Suggested treatment includes both treatment of the rickettsial infection and elimination of the fluke. (D251.9.w10)
  • Antibiotics against the rickettsial infection include tetracycline, 20 mg/kg orally every eight hours for three weeks, or oxytetracycline 7 mg/kg intravenously every 12 hours until oral dosing is tolerated or chloramphenicol, 30 mg/kg orally or intravenously every eight hours; or trimethoprim sulphadiazine 15 mg/kg orally or subcutaneously every 12 hours; or sulfadimethoxone/ormetoprim, first dose 55 mg/kg orally then 27.5 mg/kg orally once daily. (D251.9.w10)
  • Anthelmintic against the fluke: fenbendazole 50 mg/kg orally once daily for 10-14 days; or Drontal Plus (praziquantel/pyrantel/febental) according to the manufacturer's instructions. (D251.9.w10)

Prevention

• Avoid feeding salmonid fish from the Pacific Northwest, OR feed fish which have been thoroughly frozen (at least three days of freezing for large salmon). (D251.9.w10)
• Note: hatchery fish from the Pacific Northwest of North America may be transplanted for sport fishing. Cases of this disease may then occur outside the expected geographical area. It is important to be aware of the origins of fish from artificially-stocked reservoirs. (P106.2007.w9)

• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Environmental Assessment
• Treatment and Care
• Environmental and Population Management
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

• Bears (Ursidae - Bears (Family))
• Helarctos malayanus - Sun bear
• Ursus maritimus - Polar bears

(List does not contain all other species groups affected by this infectious agent)